ERC Advanced Grant: SuperMagnonics
With this prestigious grant that provides funding of more than 2.4 million euros, Prof. Hillebrands will open up a new field of research: supermagnonics. He and his team will investigate macroscopic magnonic quantum phenomena with the aim to make data processing significantly more efficient.
The award-winning concept of supermagnonics is an advancement of magnonics – a field which was already fundamentally co-developed by Prof. Hillebrands. It is based on magnetic phenomena in crystal lattices that are caused by the spin, or intrinsic angular momentum, of electrons. Immaterial spin waves (known as magnons) serve as a medium and carrier of information. As waves are able to transmit more information than electrons and heat generation can be kept at a minimum, this creates completely new means of making data processing substantially more efficient. One day this may lead to new systems of computer technology.
Discovery of a magnonic supercurrent at room temperature
Supercurrents are known physical phenomena related to the phenomena of superconductivity and superfluidity. Until now, they have only been observed at very low temperatures. A research team chaired by the Kaiserslautern physicist Burkard Hillebrands has now found first experimental evidence for a novel type of supercurrents existing at room temperature. The results that were achieved jointly with theoreticians from Israel and Ukraine, open new opportunities for applications in information technology.
The study builds on the concept of supermagnonics which was developed by Hillebrands and his team. It is an advanced concept of magnonics – a field which was already fundamentally co-developed by Hillebrands. In magnonics, magnons serve as carrier of information. The researchers studied a specific state of magnons, a magnonic Bose-Einstein condensate. This is a coherent, macroscopic quantum state of the system described by a coherent wave function. By initiating a phase gradient in this state they observed a magnonic supercurrent.
Under optimal conditions supercurrents can carry information without any loss of energy. Therefore, the present discovery is very important for the development of new technologies for logic gates that are in the focus of studies as a potential alternative to semiconductor-based data technology.
The studies were recently published in the prestigious Journal Nature Physics:
Supercurrent in a room-temperature Bose–Einstein magnon condensate, Dmytro A. Bozhko, Alexander A. Serga, Peter Clausen, Vitaliy I. Vasyuchka, Frank Heussner, Gennadii A. Melkov, Anna Pomyalov, Victor S. L’vov and Burkard Hillebrands, Nature Physics 2016, dx.doi.org/10.1038/nphys3838.
The studies were carried out at the Department of Physics of the University of Kaiserslautern are integrated into the State Research Center OPTIMAS of the State Research Initiative Rhineland-Palatinate.
What is a Supercurrent?
A supercurrent flows in a macroscopic quantum state. Such a state that can only be understood by means of quantum mechanical arguments, is characterized by a coherent wave function and it has macroscopic dimensions, e.g. it can extend over a whole device. Supercurrent transport phenomena occur when the phase of the wave function is forced into a spatial gradient. The mechanism for this is completely different from conventional electric conduction mechanisms, where a current is caused by a difference of potential.
What is a Bose-Einstein-Condensate?
Cooling a gas changes its state to the liquid or solid phase. Beside these fundamental states of matter, quantum physics describes a further state of matter called a Bose-Einstein condensate (for particles with integer spin). It can be obtained in gases of real particles as well as quasi-particles like excitons, polaritons and magnons. Similar to the swarm behavior of birds in late autumn, where individual birds migrate together in a collective flock, gas particles can constitute a collective phase with each particle having equal energy and momentum. While the observation of the condensed phase in a real particle gas requires low temperatures, it can be obtained at room temperature in the case of quasi-particle gases. This makes their investigation by far easier.